The prior art has shown an integrated connector block having a plurality of connectors for supplying power to ignition coils, as disclosed in Japanese Patent Laid-Open Publication No. Hei 9-250437. According to the structure shown in this publication, a plurality of ignition coils are provided for corresponding spark plugs mounted in the engine. These are coaxially coupled to respective coil connecting portions on a lower face of a bar-like, resin connector block member so as to be outwardly fit into the connecting portions.
Meanwhile, to enable the collective mounting of a plurality of ignition coils into their respective plug holes on the engine side, there have been proposed ignition coil assemblies that each hold a plurality of ignition coils fixedly arranged with a predetermined spacing. FIG. 20 shows one such prior art ignition coil assembly 51. A resin base member 53 supports a plurality of ignition coils 52 at locations corresponding to their respective plug holes 5d formed in the engine head cover 5. Each ignition coil 52 is fastened to the base member 53 by bolts or is integrally formed therewith by a resin molding process. The ignition coil assembly 51 is mounted on the engine head cover 5 so that the ignition coils 52 are coaxially inserted into the plug holes 5d. The ignition coil assembly 51 is then fixed to the engine by mounting bolts 53c screwed through bolt holes at lengthwise ends of the base member 53.
The problem with such a prior-art ignition coil assembly 51 is that it involves the cumbersome work of pulling out all the ignition coils 52 together from the plug holes in the engine for the service and replacement of the spark plugs as illustrated in FIG. 21. The ignition coils 52 are respectively connected to the spark plugs 6 by plug caps 52d. Pulling out all the ignition coils 52 at once requires a large force that is represented by the strength required for pulling out one ignition coil multiplied by the number of engine cylinders. Thus, the dismounting of the ignition coils 52 is hard work.
Prior art designs have attempted to solve this problem. U.S. Pat. No. 6,868,844 (Kawai) involves an ignition coil assembly that includes a plurality of ignition coils connected to respective spark plugs mounted in respective plug holes formed in the engine. Kawai includes a base member detachably mounted to the engine for supporting the plurality of ignition coils at locations corresponding to the plug holes in the engine, and a removal mechanism for allowing the base member mounted to the engine to be removed from the engine. The base member and coil assembly can be removed for carrying out desired maintenance operations such as service and replacement of the ignition coils. However, even though the plurality of coils can be removed, they sit upon the base member in Kawai. Thus, to remove the ignition coils, the base member has to be detached from the engine, so the assembly can be pulled out and the ignition coils replaced. While this allows for individual ignition coils to be replaced, Kawai does not make the removal of individual ignition coils very easy with regards to the tight spaces and low clearance required in working engines. Further, Kawai does not allow for individual ignition coils to be replaced without removing the base member and coil assembly.
Other prior art designs such as U.S. Pat. No. 6,805,086 (Kawai II) include a base member mounted to an engine with ignition coils being mounted, but adjustable, on the base plate. This allows the manufacturing precision of the plug hole pitch to be eased. U.S. Pat. No. 6,675,786 (Tsunenaga) provides an ignition coil assembly, which allows removable of only a top part of the assembly to facilitate replacement of one or more ignition coils.
United States Patent Publication No. 2008/012199 (Harbert) provides for a coil bracket screwed to a corresponding base member, whereby the ignition coils are secured to the coil bracket. To remove the coils, the coil bracket can be taken off and individual ignition coils can be serviced or replaced, or the entire multi-coil subassembly can be removed by unscrewing the mounting bracket. However, at a minimum, part of the assembly must be removed in order to access the ignition coils and remove them individually.
Thus, in prior art designs, either the base member or coil bracket must be removed in order to individually service and replace coil brackets. It is advantageous to be able to remove individual ignition coils without removing the assembly or part of the assembly from the valve cover. This can add to the speed and efficiency in which individual ignition coils can be replaced, as the assembly does not have to be removed and the replaced back onto the valve cover.
Furthermore, automobiles and other transportation devices typically have tight spaces and low clearance with which to work on the engines. Space and clearance is of the highest priority with regards to these devices and it can be advantageous to add functionality to allow for easy access and removal of ignition coils.
Other advantages that the prior art does not include is the ability to access both sides of the coil bracket, as it can be advantageous, but not necessary, to access both sides of the coil bracket for removal and replacement of the ignition coils. Allowing access to both sides of the coil bracket can increase the speed of removal of the ignition coils. Also allowing access to both sides of the coil bracket allows for the coil bracket to slide off the base member.
Other advantages are to add thermal protection to minimize the transfer of heat from the valve cover to the ignition coils and coil bracket. As the engine radiates heat when it is in operation, it is advantageous to have a mechanism that separates the ignition coils from the valve cover. Heat from the engine will thus be transferred to the coil bracket and ignition coils via convection rather than conduction, resulting in the coil bracket and ignition coils becoming less hot.
What is desired, therefore, is to provide an ignition coil assembly that permits easy removal of individual ignition coils without removing part of or the entire coil assembly from the engine. It is desirable to provide a mechanism whereupon the ignition coils are mounted onto a coil bracket which can rotate, allowing for easy access to the ignition coils for removal and replacement of the ignition coils. It is also desired to be able to remove the coil bracket, so that a plurality of ignition coils mounted on the coil bracket can be removed and replaced. Further, it is desired for a locking mechanism that locks the coil bracket to the base plate, thus locking the ignition coils into place.